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02-25-2010, 12:41 AM   #1
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PTTL and the K7

Just purchased the K7 after trading in my K20D, and have noticed that the results of shooting PTTL wirelessly differ from those of the K20D.

I can't seem to get the proper exposure when shooting wirelessly with the K7.. Beautiful results if the flash is attached to the camera, but as soon as I change over to wireless, NG..

Set ISO to auto (100-800), Program, flash set to wireless slave, camera set to act as controller flash only in wireless, K7 and AF360-FGZ set to same channel, slave mode 1. Pictures have blown out highlights..

If I change the ISO to 100, I get better results. I don't recall having this issue with the K20D however..

Wondering if anyone else has had a similar experience...

02-25-2010, 01:02 AM   #2
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I reported this some months ago...
It seems like the on-board flash minimal output is really high in controller mode (there is always a small flash in controller mode, even with the k20, to trigger the slave), way higher than the minimum output it's capable of.
To check this, in manual mode with a fairly high iso, just go back and forth between the wireless controller mode (without an external flash around!) and the on-board only mode... You'll see that the pic is clearly overexposed in controller mode...

I bought a nikon SG-3IR to screen the on-board flash, and it's back to normal...
02-25-2010, 03:30 PM   #3
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Tiny bit confused

I bought a nikon SG-3IR to screen the on-board flash, and it's back to normal.

I'm not sure I understand the above... "screen the on-board flash".. and it's back to normal ?
02-25-2010, 03:44 PM   #4
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"Back to normal" compared to previous models, where the controller mode made the on-board flash nearly invisible...

The nikon SG-3ir is a little accessory mounted on the flash shoe that occults the on-board flash.


02-27-2010, 06:31 AM   #5
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I'm not having this problem with my K-7 and Metz 48 AF-1.
02-27-2010, 09:18 AM   #6
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MattDM, try the following : put your k7 in wireless controller mode (without using the Metz), select a moderate iso/aperture value (something around 400iso & f/2.8), and snap a pic inside...

You'll see that the on-board flash has a visible effect on the pic, when it should not! And the K20 does not have this effect, its output being really damped in controller mode...
02-27-2010, 02:46 PM   #7
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Hmmm, yeah, okay, I have to change my answer. I did the experiment you suggested, and then another one:

I set up an object so that direct flash would cast an obvious shadow. Then I set the Metz remote at a sharp angle, so that the shadow it casts is obviously different.

At f/2.8, there's clearly a shadow cast by the control flash, and barely a discernable difference between "controller" and "master" settings. At f/8, there's still a faintly visible shadow even in controller mode, but the difference between the two is far more pronounced.
02-27-2010, 03:01 PM   #8
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Yeah, what is strange is that they nailed it just right with the K20... The on-board flash was nearly invisible till 800 iso, f/1.4...

Here, the wireless controller mode is nearly crippled as it is... Hell, it can even be more powerful than used in standard mode!

You can try this : find the point where you start to have an blabant overexposure with the flash in controller mode, then use it in standard, non-wireless mode : you'll see that it can indeed be fired at a lesser output, but for an unknown reason, Pentax choose to set it quite high in controller mode...

Maybe for a outdoor-under-full-sun use?

02-27-2010, 03:06 PM   #9
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I should add that I'm still not seeing issues with overall exposure problems in wireless — that part of my answer still stands.

It is odd that things would change from the K20D. Flash power and everything are the same. I wouldn't be at all surprised if your guess is right, and that they upped the power to address complaints about P-TTL reliablility. (Something I also had no issue with.)

Anyone asked Pentax customer service about this?
02-27-2010, 03:33 PM   #10
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Yep, I'm with you here : Pentax really solved the P-TTL bugs with the K7...
02-27-2010, 04:45 PM   #11
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Can you give more details about the environment your shooting?
How close are you (the camera) to the subject?
How close are the remote flashes.
Does the subject have specular highlights (PTTl is/was notorious for going haywire on even the smallest of specular highlights in the scene)

Obviously the onboard flash must fire to notify the remote flashes to fire so there is no helping some amount of light being produced.
The closer you are to the subject, the more effect the onboard controller flash will have (inverse square law). Back away and use a longer focal length to help avoid the control flash being seen so much.

Comparing same scheme with both K10D and K7, the resulting image is quite near identical.
Camera about one or two feet from subject to ensure control flash will cast a shadow.
AF-540FZG about one foot away hitting at an angle.
The control flash creates a slight shadow on the wall six inches behind the subject.

Setting onboard flash to fire in wireless mode (master) shows a HUGE difference.

Options:
1. Get back further.
or
2. Set your aperture up to cut down on flash effect -- will require your remote flashes to be ratcheted up to compensate. This will make a greater difference between your flash and the controller onboard flash and therefore cause the effect of the controller to be less noticeable or even negated.

or
3. Block the controller or redirect it with opaque white paper.
I have in the past created my own method of blocking the flash from the subject in front of me... I put my hand in front of the flash. Blocks light from affecting the scene but is still seen by the remote flashes. The device shown above looks like it would be a lot more reliable. :-)

[edit]
just checked... even a tiny specular highlight still throws off the K7 PTTL. So PTTL will still be useless in most cases where you cannot completely control the environment -- such as with people who might have an ear ring or other jewelry, or pets with tags/collar rings, etc... Argh!
Doesn't affect your issue, but someone said K7 sorted out some PTTL bugs. Unfortunately not this one. (not a bug per-se, but highly annoying behavior!)
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